Battle of Fromelles marked in France

More than 2000 Australians have gathered in a small French village on a hot summer's day to mark the centenary of the worst day in Australian military history.

They joined French locals and dignitaries at the Pheasant Wood War Cemetery at Fromelles on Tuesday to commemorate the 14-hour battle on July 19-20, 1916.

In the first major engagement by Australians on the Western Front the 5th Division was torn apart by German shelling and machine-gun fire in a disastrous assault on well-prepared German lines.

The Battle of Fromelles resulted in more than 5500 Australian casualties, including more than 1900 dead as the Australians were repulsed in action meant to draw German reserves away from the Somme where the British had launched a major offensive.

Tight security was in place at Fromelles on Tuesday, with more than 100 gendarmes on guard and airport-style security in place in the wake of the Paris and Nice terror attacks.

At the end of the service, six new headstones were unveiled on the graves of previously unnamed Australian soldiers who were killed at Fromelles and whose remains have recently been identified.

They included a linesman and father of two from Bundaberg, a quarryman from Sydney, a bread carter from Geelong, a Queensland miner, a Sydney barman and a South Australian labourer.